1. Field of the Invention
The present invention relates to a complex-type article conveying apparatus that serves an effective measure for efficiently automatizing conveyance between steps of, for example, a press processing that includes several steps, wherein a work is taken out of a press machine in a preceding step, and moved to and set in a press machine in the next step.
2. Description of the Related Art
A thin steel sheet-pressed form having a three-dimensional free-form surface, such as one used as an exterior sheet member of a motor vehicle, is shaped from a flat sheet material through several processing steps, such as drawing, exterior shape punching, bending, piercing and the like.
During such a press process, it is necessary to perform an operation of taking a work out of a small clearance between an upper die and a lower die of each step and conveying the work to and setting it into a small clearance between an upper die and a lower die of the next step (hereinafter, this operation will be referred to as "inter-step conveyance").
Various mechanisms have recently been developed for automatizing the inter-step conveyance for the purpose of improvements in productivity, quality and safety and the like.
The construction of a conventional technology developed for such a purpose (disclosed in Japanese Utility Model Laid-Open No. Hei 4-42390) will be described below with reference to FIGS. 13, 14, 15 and 16.
Referring to FIG. 13, a six-axis multi-joint automatic motion mechanism 101 is designed so that shafts 103-108 are automatically driven in their respective rotating directions, and stopped and controlled in rotational angle in accordance with pre-instructed amounts and timings.
As shown in FIG. 15, a linear shaft body 102 is provided with a linear reciprocating body 110 that moves along the linear shaft body 102. The linear reciprocating body 110 is driven, stopped and position-controlled over substantially the entire length of the linear shaft body 102. A work holding device 111 is guided by the linear reciprocating body 110 to move back and forth along the linear shaft body 102.
As shown in FIG. 16, the work holding device 111 holds a work by suction due to negative pressure air. The work holding device 111 is detachably engaged with a base 119 by hooking a hook portion 127 formed on one end of the work holding device 111 onto the corresponding end of the base 119, and engaging the opposite end of the work holding device 111 with the corresponding end of the base 119 using a lock mechanism 121 formed of a spring 122, a slide block 123, an unlocking piece 124 and a guide groove 125. Both the base 119 and the holding device 111 have ends of negative pressure air channels communicating with suction cups 128 of the holding device 111. The channel ends of the base 119 and the holding device 111, facing each other, are sealed from external air by deflection of a seal packing 129 disposed on the base 119.
The operation of this conventional technology will be described below.
Referring to FIGS. 13 and 14, to take out a work, a forward half portion of the linear shaft body 102 (a left-side half portion in FIG. 13) is inserted into a clearance between an upper die 117 and a lower die 118 of a press machine 115 of a preceding step to move a forward end thereof to a position over the work 109 placed on the lower die 118.
The linear shaft body 102 is subsequently moved downward by operations of the rotating shafts 103-108, until the holding device 111 contacts the work 109, so that the holding device 111 holds the work 109.
The linear shaft body 102 is raised to a position M over the lower die 118 in such a manner that both the work 109 and the linear shaft body 102 do not interfere with the upper die 117 nor the lower die 118, thereby completing the takeout operation.
Then, to move the taken-out work 109 to a position immediately over a lower die 132 of a press machine of the next step, a rear end portion of the linear shaft body 102 (a right-side end portion in FIG. 13) is moved linearly from the takeout completed position to a position N over the lower die 132.
During this movement, the holding device 111, assuming a position near a forward end portion of the linear shaft body 102 at the time of completion of the takeout operation, moves to a rear end portion of the linear shaft body 102, through guidance by the linearly reciprocating body 110 moving in accordance with pre-instructed motion, while holding the work 109.
Then, the rotating shafts 103-108 are operated to lower the linear shaft body 102, and the holding device 111, having moved to the rear end portion of the linear shaft body 102, opens to allow the work 109 to fall onto the lower die 132.
After the work 109 is set in, the apparatus returns to the previous position by reversely following the loci of movements up to the setting of the work 109, thereby completing the inter-step conveying operation.
There is a case where during the inter-step conveyance, two works are discharged from a single press machine and transferred to different positions (that is, a work at a first position in the press machine is transferred to a second position outside the press machine, and the other work at a third position in the press machine is transferred to a fourth position outside the press machine).
In such a case, the inter-step conveying apparatus needs to perform the takeout-transfer action twice since the inter-step conveying apparatus is able to hold only one work at a time. Therefore, the conventional art has a problem of a long operating time of the inter-step conveying apparatus.
Accordingly, it is an object of the present invention to reduce the operating time of an inter-step conveying apparatus in a case where two works are discharged from a single press machine and transferred to different positions.
Furthermore, there is another case where press dies for two steps are disposed in a single press machine with a work-conveying in-die transfer apparatus provided between the dies, in order to reduce the number of press machines.
The in-die transfer apparatus moves a work from a location X in the press machine to a location Y in the same press machine. Thereby, it becomes possible to perform two pressing steps in a press machine by pressing a work at the location X in the press machine, moving the work to the location Y in the same press machine, and pressing the work at the Y location.
However, such in-die transfer apparatuses are provided as dedicated apparatuses in individual press machines, or an in-die transfer apparatus is dedicated to the press dies for two steps disposed in a single press machine, thereby producing a problem of increased costs of dedicated equipment.
Accordingly, it is another object of the present invention to enable a press machine to perform two pressing steps without an increase in dedicated equipment for press machines or press dies.
It is still another object of the present invention to enhance the general versatility of a conveying apparatus by facilitating replacement of individual holding devices.
It is a further object of the present invention to make it possible to set one work to a desired position while holding and conveying another work.